26 BULLETIN 1428, U. S, DEPARTMENT OF AGRICULTURE 
The shortest larval period observed was 39 days from the date 
of hatching to assumption of the prepupal state, or 48 days to the 
date of pupation. This larva hatched on June 20, 1922, and pupated 
August 7, 1922. It was fed on corn. 
The longest larval period observed of those reared on favorable 
food was 414 days. This larva was also reared on corn. 
The phenomenally long larval period, noted first by Kirkup (17) in 
1812 and more recently by McColloch (22) in 1922, was probably 
due to unfavorable food or environmental conditions. Kirkup re- 
corded the case of a single larva which fed for more than 15 months 
before transforming, its food apparently consisting only of the al- 
mond nut in which it was found ; how long it had been feeding before 
discovery can not be predicted but it might have been several months. 
McColloch found that larvae lived from 628 to 1,248 days before 
transforming, the larvae being fed wheat, wheat bran, and flour. 
NUMBER OF MOLTS 
The cadelle larva usually molts either three or four times, al- 
though five, six, and seven molts are not unusual when the larval 
period is long. If for any reason the larva*l period is prolonged 
beyond its normal length, many more molts may occur. The writers 
observed one larva to molt nine times and McColloch observed an- 
other to molt no less than eleven times. 
Observations show that the larvae that hatch in the early spring, 
if supplied with favorable food, molt only three times. Of those 
that hatch later in the year, about one-half molt three times and 
the rest four times, even though food supplies and other conditions 
are apparently identical. Larvae that winter over, although ap- 
parently fully grown, sometimes start feeding again in the spring 
and may molt once or twice in the spring before transforming. 
When possible the larva seeks a sheltered place in which to molt; 
at other times, when breeding in flour, it comes to the surface to molt. 
LENGTH OF LARVAL IN STARS 
The different larval instars naturally vary considerably in length 
at different times of the year, but during the summer months they 
are more or Jess uniform. Their average lengths in summer are : 
First instar, about 11 days; second instar, about 11 days; third instar, 
about 14 days; fourth instar, about 18 days; and fifth instar, when 
it occurs, about 11 days. A more comprehensive idea of the relative 
lengths of these instars and the variation in them can be obtained 
by a study of Tables 7 and 8, which give complete life-history data 
of a number of individuals. 
PUPATION 
After attaining its growth the larva becomes restless and wanders 
about seeking a place of safety in which to undergo the transforma- 
tions to the pupal and adult forms. It prefers to burrow into a 
piece of soft wood, hollow out a small chamber, and close up the 
open end with a cement made from the borings mixed with a larval 
secretion. It occasionally crawls between two boards and forms its 
cell between them, especially if the boards are of hard wood (fig 13). 
